The long range aim of this project is to determine the neural basis of adaptive mechanisms responsible for maintaining appropriate performance levels in the oculomotor system. Mechanisms currently under study relate to 1) the gain of the vestibulo-ocular reflex, 2) the pulse-step ratio of saccadic eye movements and 3) the gain of accommodation-vergence. One series of experiments showed that bilateral flocculectomy in the monkey results in severe deficits in the first two of these adaptive mechanisms and also in the optokinetic response. A second series demonstrated that changes in the gain of the vestibulo-ocular reflex result in parallel changes in the optokinetic response. A third series showed that the compensatory eye movements generated by the vestibulo-ocular reflex following sudden disturbances of the head are essentially uninfluenced by ongoing tracking behavior in the short-term; however, prolonged foveal pursuit during head movements - in the absence of any peripheral retinal slip - can gradually elicit long-term changes in the gain of the vestibulo-ocular reflex.